My dad's new F-450 came in a few weeks ago and we just got back from a roap trip to Colorado. I have to say its a very nice truck and the new 6.4L is pretty nice, feels like it has plenty of power and its pretty dang responsive compared to the '02 F-250 with the PSD. I dont have any pictures of the new rig right now...but I can try to get some up if anybody is really interested.

Dad bought this truck with the intentions of hauling an RV trailer behind it (plan to purchase that within the next year or two), and so he had it equipped with the 4.88 gears. Unfortunately, this equates to not so great fuel mileage. It gets low 10s on the highway and about 11.4 in town.
He is considering having the gears swapped out to the 4.30s in the hope of getting some better fuel mileage until they buy a trailer.
Would this be worth it, what kind of MPG gains would be realistic to expect by going to the lower gears? Are there lower gears available for this rearend than the 4.30s (4.30 is the lowest available from Ford)? I think he is missing the '02 F250 in this regard, it gets about 18MPG on the highway.

Also, he is thinking about having the dealership do the swap...I told him to be sure to look around because its definitely going to be more expensive there, but then again I dont know if there are many places that will handle this size truck... they are in the Dallas/Ft Worth area if anybody knows of a good place.


It has 19.5" wheels and the tires on it are screaming to be upgraded...the 19.5" wheel is an odd size for me so I dont really know any good resources, so some info there would be great as well.

Also can anybody give me any experiences with GearVendors overdrive units?

Thanks for any insight.

 

Got a pic or two:

 

It would be quite a waste to switch to 4.30's then back to the 4.88's just a year or so down the road. The gears/install would probably be in the $1500-$1800 range. IMO, the difference in mpgs wouldn't be worth paying $3000+ to switch gears twice in a matter of two years, plus you're only talking maybe a couple miles per gallon difference with 4.30's over the 4.88's.

 

Yeah switching between those 2 gears would maybe yield 1-2 mpg difference. A single swap (1 time) for a 4wd is going to run a BARE MINIMUM of $1,200, but I would think even more for that truck.

IMO, take the $1,200+~, and use it to upgrade the intake, exhaust, and tuning. The cost would be the same, and the end result would be the same increase (or likely even better) in increased MPG, AND increased power galore.

Just a thought.

 

Well, I have to say I know it wouldnt really be worth it. I dont think my dad has really looked that hard at it yet so Im sure he doesnt actually realize just how much it will cost right now (I was telling him to expect ~$1000+, but that was the price I was always told for an F150, so I wouldnt be surprised if the 450 was a bit more).

How many MPG increase do you think would be reasonable to expect? 2 or 3? More than that? 15 on the highway would be great...

 

I have thought about that as well. I was going to suggest an EDGE tuner to him. I know a custom tune is the best, but the EDGE would work well for diplaying info as well, I think he would prefer that look to gauges. Is the EDGE's info (EGTs, oil temps, etc) accurate?
I also noticed that SCT has the new Livewire...I havent seen anything about it, is it any good?

 

Can anybody tell me what type of differentials the 450 uses?

 

Well first off... the 6.4l TTD is known for bad fuel mileage at the beginning... but after 10k on the clock, it should be improving.

Switching from 4.88s to 4.30s is like me considering going from 3.73s from 4.10s. Just stupid. I doubt I'd notice any difference in fuel mileage.

Also, the amount of payload the 4.88s can handle is sick... why you'd give that up on 1-2 mpgs is beyond me. IF he can afford to drive the truck, then why did he intend to buy it?!

I don't mean to sound derogatory... but honestly don't complain, because the amount of money you'd spend on a stupid gear swap would NEVER pay off for itself in the long run in your situation.

But hey, it's you Dad's truck... let him decide.

Personally, I'd be more worried about getting new rims for it rather than a set of gears.

 

Must not have heard about how easily the Edge Juice has been able to wipe out the 5R110 behind the 6.0L. Pure and simple, any module is not going to be a good idea. You need something with trans controls of which modules don't have, at least in the true form. The SCT is a much better choice, though your dad needs to be aware that any chip/module/programmer can and will void his warranty. I would suggest that he look for a Gear Vendors or US Gear unit. The root cause of the issue is the higher rpms while at highway speed. Dropping those rpms is the key, which an overdrive unit can do while still maintaining highway speed. I would say that he can expect 15mpg highway at MOST, but I'd actually plan on less.


How big of an RV is he planning on buying that he needs 4.88 gears? That thing has to be the size of a house. The F550s we run at work have 4.88 gears only because we regularly pull 26-28k gross (yes that is overweight). I'll be with a typical 5th wheel RV he wouldn't be passing 20k gross which 4.30 gears are more than enough for. I never understood why people would order these trucks with 4.88 gears only to pull RVs.

 

When people have more money than they should with no automotive experience, they tend buy stuff like this.

Like someone I know, that thinks they know everything about cars and trucks tried to convince me that 3.08's are better than 4.10's are at pulling weight with the same engine. I said... oooohhhkaayyyy.... and I just laughed. So what did they buy?! A truck with 3.08's... without a LS! They actually thought having a $200 limited slip was bad. Fine... it's your money... don't complain to me when your truck is feeling sluggish.

 

A friends husband bought a F450 4X4 with the 4.30 gears for towing his 30 gooseneck. He said that running empty on the highway at 60 he gets 12.5-13mpg, empty at 70 he get 10. Towing 20K he said that he usually goes 60, even on the interstate, and has been seeing 10.5-11. He said that he tried running 65 and he was in the 9's.

From what I have heard and read, the 6.4L's are just like the 6.0L's, the mileage with them just plain suck. My father has a 05 F350 SC, DRW, FX4, 6.0L tow boss with 4.30 gears, and he only sees 13 running empty and around 11 towing a 14K 5th wheel, both at around 60-65mph. When the thing isn't eating injectors.

Your dad may love the power of the 6.4L, but there is no way he will see anything close to the mileage of his 7.3L.

Also DO NOT GET AN EDGE!!! The Edge Juice will burn out your tranny if you run it long enough. Also Ford has become very mod unfriendly, especially after all the 6.0L problems. I have heard from a couple different sources that dealers have been told to void drivetrain warranty on any modded 6.4L's.

 

Thanks for the informative posts so far.

I honestly dont know how big of an RV they plan to get, they are still looking at them and as I said at first, they are still a ways out from actually buying one (1 to 2 years at the earliest). Its going to be on the order of 30+ feet long with the possibility of a Jeep or similar vehicle behind that (F-450 crew cab dually with 8 foot bed isnt exactly a trail friendly vehicle).
Based on what my dad was telling me, the 4.30s would have probably done the job but he wanted the extra capability to be on the safe side...I agree that this was probably overkill, but he never really asked for my input and this was his baby so he got what he wanted and so here we are.

Thanks for the tips on the EDGE, I know I dont know much about tuners (or the PSDs in general for that matter), and that why I ask you folks. I may just forget about a tuner, I know he will want some gauges of some sort on it by the time he gets the trailer and all, but I thought it would be nice if he could get something that would display the info as well as handle tunes. Sounds like there isnt really anything out there yet that will fit that bill without killing the drivetrain.

This isnt really an issue about diesel being expensive and the cost being too high, although cheaper is always better (if he really wanted something that got great MPG, he wouldnt have considered an F-450 for very long). The hopes for higher MPG for my dad are really the hopes of getting more distance to a single fillup. This thing has a 39 gallon tank, so even 2 MPG improvement means an extra ~80 miles per fillup. Of course once its pulling a load, there arent any expectations for high MPG.

 

Does he intend on running a goose neck? If not, get a hard tonneau cover. that would add 1+ MPG easily, and give a nice locked storage area too.

 

I hate to burst your bubble... but you are complaining about trying to gain an extra 2 mpg on a F450... Please...

I didn't buy my truck for mpg, I bought knowing I'd be getting poor gas mileage. Even though I usually get a whopping 22 mpg.

But your Dad just shelled out X amount of dollars on a VERY heavy truck. He should be lucky it's getting what it's getting. It could be worse!

And don't get a tuner... it's a wonderful way to void your warranty quick on the 6.4l. If you do add one... you are just asking for trouble.

Besides, no matter what diesel engine you buy new these days... you are lucky, and I MEAN lucky to get 17 mpg.

 

Why would you want to detune your performance - don't the 6.4L F450's and up have 'only' 325hp and 600lbs compared to the 6.4L F350's 350hp and 650lbs? I would think that the F450 with 4.88 rear is about the same as the F350 with 4:30 rear when you look at torque to the ground...

The responsiveness - snappier feel - between the 02 F250 and 08 F450 may probably be due to gearing (SRW w/ 3.73 vs DRW w/ 4.88)

Gas mileage issue - are you kidding?!?!